1. Field of the Invention
The present invention relates to isolated polypeptides having endoglucanase activity and isolated polynucleotides encoding the polypeptides. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the polynucleotides as well as methods for producing and using the polypeptides.
2. Description of the Related Art
Cellulose is a polymer of the simple sugar glucose covalently bonded by beta-1,4-linkages. Many microorganisms produce enzymes that hydrolyze beta-linked glucans. These enzymes include endoglucanases, cellobiohydrolases, and beta-glucosidases. Endoglucanases digest the cellulose polymer at random locations, opening it to attack by cellobiohydrolases. Cellobiohydrolases sequentially release molecules of cellobiose from the ends of the cellulose polymer. Cellobiohydrolase I is a 1,4-beta-D-glucan cellobiohydrolase (E.C. 3.2.1.91) activity which catalyzes the hydrolysis of 1,4-beta-D-glucosidic linkages in cellulose, cellotetriose, or any beta-1,4-linked glucose containing polymer, releasing cellobiose from the reducing ends of the chain. Cellobiohydrolase II is a 1,4-D-glucan cellobiohydrolase (E.C. 3.2.1.91) activity which catalyzes the hydrolysis of 1,4-beta-D-glucosidic linkages in cellulose, cellotetriose, or any beta-1,4-linked glucose containing polymer, releasing cellobiose from the non-reducing ends of the chain. Cellobiose is a water-soluble beta-1,4-linked dimer of glucose. Beta-glucosidases hydrolyze cellobiose to glucose.
The conversion of cellulosic feedstocks into ethanol has the advantages of the ready availability of large amounts of feedstock, the desirability of avoiding burning or land filling the materials, and the cleanliness of the ethanol fuel. Wood, agricultural residues, herbaceous crops, and municipal solid wastes have been considered as feedstocks for ethanol production. These materials primarily consist of cellulose, hemicellulose, and lignin. Once the cellulose is converted to glucose, the glucose is easily fermented by yeast into ethanol.
Roy et al., 1990, Journal of General Microbiology 136: 1967-1972, disclose the purification and properties of an extracellular endoglucanase from Myceliophthora thermophila ATCC 48104. Chemoglazov et al., 1988, Biokhimiya 53: 475-482, disclose the isolation, purification, and substrate specificity of an endoglucanase from Myceliophthora thermophila. Klyosov et al., 1988, Biotechnology Letters 10: 351-354, disclose a thermostable endoglucanase from Myceliophthora thermophila. Guzhova and Loginova, 1987, Prikladnaya Biokhimiya I Mikrobiologiya 23: 820-825, disclose cellulolytic enzymes from Myceliophthora thermophila. Rabinovich et al., 1986, Bioorganicheskaya Khimiya 12: 1549-1560, disclose the purification and characterization of an endoglucanase from Myceliophthora thermophila. Svistova et al., 1986, Mikrobiologiya 55: 49-54, disclose the regulation of cellulose biosynthesis in Myceliophthora thermophila. Bhat and Maheshwari, 1987, Applied and Environmental Microbiology 53: 2175-2182, disclose the activity of components of the extracellular cellulose system of Myceliophthora thermophila. Klyosov et al., 1987, Prikladnaya Biokhimiya I Mikrobiologiya 23: 44-50, disclose a thermostable endoglucanase from Myceliophthora thermophila. Jorgensen et al., 2003, Enzyme and Microbial Technology 32: 851-861, and Thygesen et al., 2003, Enzyme and Microbial Technology 32: 606-615, disclose cellulose-degrading enzymes from Penicillium brasilianum IBT 20888.
It would be an advantage in the art to identify new endoglucanases having improved properties, such as improved hydrolysis rate, better thermal stability, reduced adsorption to lignin, and ability to hydrolyze non-cellulosic components of biomass, such as hemicellulose, in addition to hydrolyzing cellulose. Endoglucanases with a broad range of side activities on hemicellulose can be especially beneficial for improving the overall hydrolysis yield of complex, hemicellulose-rich biomass substrates.
It is an object of the present invention to provide improved polypeptides having endoglucanase activity and polynucleotides encoding the polypeptides.